Efficacy of a therapeutic protein can be limited by an unwanted immune reaction to the therapeutic protein. For monoclonal antibodies, a number of techniques have been developed in attempts to reduce the human anti-murine antibody (HAMA) response. In general, these approaches aim to reduce the mouse genetic information in the final antibody construct while increasing the human genetic information. Examples of such approaches are chimeric, humanized and fully human monoclonal antibodies (mAbs).
Chimeric antibodies contain regions derived from different animal species, such as a murine immunoglobulin (Ig) variable region and a human Ig constant region. Infliximab (sold under the brand name REMICADE®) is a chimeric IgG1κ monoclonal antibody that specifically binds human tumor necrosis factor-α (TNFα). Infliximab has human constant regions and murine variable regions. The heavy chain variable region (VH) of infliximab has 119 amino acids; the light chain variable region (VL) has 107 amino acids. See, U.S. Pat. Nos. 6,277,969, 6,284,471, 6,790,444, and 6,835,823, all of which are incorporated herein by reference.
TNFα can be produced by a wide variety of cells, but activated macrophages constitute the most abundant source of this factor (Vassalli, Ann. Rev. Immunol. 10: 411-452 (1992)). TNFα is a soluble homotrimer of 17 kD protein subunits (Smith, et al., J. Biol. Chem. 262: 6951-6954 (1987)). A membrane-bound 26 kD precursor form of TNFα also exists (Kriegler, et al., Cell 53: 45-53 (1988)).
TNFα causes pro-inflammatory actions which result in tissue injury, such as inducing procoagulant activity on vascular endothelial cells increasing the adherence of neutrophils and lymphocytes, and stimulating the release of platelet activating factor from macrophages, neutrophils and vascular endothelial cells (Pober, et al., J. Immunol. 136: 1680-1687 (1986); Pober, et al., J. Immunol. 138: 3319-3324 (1987); Camussi, et al., J. Exp. Med. 166: 1390-1404 (1987)).
The numerous biological effects of TNFα and the closely related cytokine, TNF (also known as lymphotoxin), are mediated by two TNF transmembrane receptors, the p55 and p75 receptors (Hohmann, et al., J. Biol. Chem. 264: 14927-14934 (1989); Engelmann, et al., J. Biol. Chem. 265: 1531-1536 (1990)). Extracellular domains of TNF receptors derived by proteolytic cleavage inhibit TNF functions (Kohno, et al., Proc. Natl. Acad. Sci. U.S.A. 87: 8331-8335 (1990)). TNFα is associated with infections, immune disorders, neoplastic pathologies, autoimmune pathologies and graft-versus host pathologies (Cerami, et al., Immunol. Today 9: 28-31 (1988); Oliff, et al., Cell 50: 555-563 (1987); Piguet, et al., J. Exp. Med. 166: 1280-1289 (1987)). Dysregulation and, in particular, overproduction of TNFα has been implicated in a variety of human diseases including sepsis, cerebral malaria, and autoimmune diseases such as multiple sclerosis, rheumatoid arthritis (RA), systemic lupus erythematosus, and Crohn's disease, as well as cancer (reviewed in Zhang and Tracey, The Cytokine Handbook, Thomson A W (ed). pp 517-548 (1998)). TNFα can mediate cachexia in cancer, infectious pathology, and other catabolic states (reviewed in Tracey, et al., Ann. N.Y. Acad. Sci. 587: 325-331 (1990)).
Neutralizing anti-TNFα antibodies that inhibit TNFα activities are useful in treating and/or diagnosing TNFα-mediated diseases. Infliximab has been approved in the United States for treatment of ankylosing spondylitis, Crohn's disease, psoriatic arthritis and rheumatoid arthritis. It can also effectively treat other disorders or symptoms of various immune and autoimmune pathologies as well as inflammatory diseases, such as systemic lupus erythematosus, thyroidosis, graft versus host disease, scleroderma, diabetes mellitus, Grave's disease, sarcoidosis, chronic inflammatory bowel disease, ulcerative colitis, disseminated intravascular coagulation, atherosclerosis and Kawasaki's pathology. See, U.S. Pat. Nos. 5,656,272, 5,698,195, and 5,919,452, all of which are incorporated herein by reference.
It has been reported that antibodies to infliximab have been observed in some treated patients (Targan et al., N. Engl. J. Med. 337: 1029-1035 (1997); Maini et al., Arthritis Rheum. 41: 1552-1563 (1998)). Accordingly, in order to potentially diminish the incidence of anti-infliximab antibodies in treated patients, it is desirable to reduce the amount of murine amino sequences present in the molecule.